Add missing uint32 type to folly::ProgramOptions::gFlagAdders

Summary: Absence of "uint32" type in gFlagAdders map breaks all apps that use gflags of this type (i.e. define a flag with "DEFINE_uint32").

Reviewed By: WillerZ

Differential Revision: D5286720

fbshipit-source-id: c02bd959cb9ea9a47fba1e01429181ba09edf5dd

folly/experimental/ProgramOptions.cpp

@@ -237,6 +237,7 @@ const std::unordered_map<std::string, FlagAdder> gFlagAdders = {
   X("bool",   bool)
   X("int32",  int32_t)
   X("int64",  int64_t)
+  X("uint32", uint32_t)
   X("uint64", uint64_t)
   X("double", double)
   X("string", std::string)